Supporting handover of mobile terminal

ABSTRACT

The present invention relates to supporting a handover of a mobile terminal. Preferably, the present invention performs a scan of a neighboring network different from a current network of the mobile terminal to determine the presence of an accessible link of the neighboring network for performing a handover, wherein the mobile terminal comprises a heterogeneous network handover module that is configured to provide convergence of information from at least one network interface module associated with one of a homogeneous and heterogeneous network into a unified presentation. An information message is then received from the neighboring network, wherein the information message comprises an information element associated with whether the neighboring network is capable of communicating with the heterogeneous network handover module of the mobile terminal.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.10-2005-0029750, filed on Apr. 9, 2005, Korean Application No.10-2005-0081990, filed on Sep. 3, 2005, and Korean Application No.10-2006-0020298, filed on Mar. 3, 2006, the contents of which are herebyincorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to communicating information for mediaindependent handover (MIH), and more particularly, to supportinghandover of a mobile terminal.

BACKGROUND OF THE INVENTION

A broadband wireless access system according to a related art will beexplained in general as follows. Unlike the conventional 2G or 3G mobilecommunication systems, an IEEE 802.16e system, for which internationalstandardization of a broadband wireless access system is in progress, isnot provided with a hierarchical structure for a home location register(HLR), a visitor location register (VLR), a mobile switching center(MSC), a base station controller (BSC), a radio network controller (RNC)and the like. However, the IEEE 802.16e system includes a mobilesubscriber station (MSS) as a mobile terminal, a base station (BS) andan authentication service authorization (ASA) as an authenticationmanaging server. Furthermore a common physical layer (PHY) and a mediumaccess control (MAC) layer are defined between the base station and themobile subscriber station.

FIG. 1 is a diagram of a frame structure for an orthogonal frequencydivision multiple access (OFDMA) physical layer in a broadband wirelessaccess system. Referring to FIG. 1, a downlink subframe starts with apreamble used for synchronization and equalization in a physical layer.Following, the preamble is a broadcast-formatted downlink map (DL-MAP)message defining positions and usages of bursts allocated to a downlinkand uplink and a frame control header (FCH). An uplink map (UL-MAP)message follows the DL-MAP and FCH to define a structure of an entireframe.

Examples of DL-MAP and UL-MAP messages are shown in Table 1 and Table 2,respectively.

TABLE 1 Syntax Size Notes DL-MAP_Message_Format( ) {  Management MessageType = 2 8 bits  PHY Synchronization Field variable See appropriate PHYspecification.  DCD Count 8 bits  Base Station ID 48 bits   Begin PHYSpecific Section { See applicable PHY section.   for(i=1; i <= n;i++) {For each DL-MAP element 1 to n.    DL-MAP-IE( ) variable Seecorresponding PHY specification.    }   }  if !(byte boundary) { Padding Nibble 4 bits Padding to reach byte boundary.   }  }

TABLE 2 Syntax Size Notes UL-MAP_Message_Format( ) {  Management MessageType = 3 8 bits  Uplink Channel ID 8 bits  UCD Count 8 bits  AllocationStart Time 32 bits   Begin PHY Specific Section { See applicable PHYsection.   for(i=1; i <= n;i++) { For each UL-MAP element 1 to n.   UL-MAP-IE( ) variable See corresponding PHY specification.    }   } if !(byte boundary) {  Padding Nibble 4 bits Padding to reach byteboundary.   }  }

In a burst mode physical layer, a DL-MAP message defines usages ofbursts allocated to a downlink interval and a UL-MAP message definesusages of bursts allocated to an uplink interval. For informationelements configuring the DL-MAP message, as shown in Table 3, a downlinktraffic interval is identified at a user end by a downlink intervalusage code (DIUC), a connection identifier (CID) and burst positioninformation (e.g. subchannel offset, symbol offset, subchannel no., andsymbol no.). For information elements configuring the UL-MAP message, asshown in Table 4, usage is determined by an uplink interval usage code(UIUC) per connection identifier (CID). A position of a correspondinginterval is regulated by duration. In this case, a usage per interval isdetermined according a UIUC value used in the UL-MAP. Each intervalstarts at a point having some distance from a previous informationelement (IE) start point regulated by the UL-MAP IE.

TABLE 3 Syntax Size Notes DL-MAP_IE( ) {  DIUC 4 bits  if (DIUC == 15) { Extended DIUC variable dependent IE  } else {  if (INC_CID == 1) TheDL-MAP starts with { INC_CID = 0. INC_CID is toggled between 0 and 1 bythe CID-SWITCH_IE( ).  N_CID 8 bits Number of CIDs assigned for this IE for (n=0; n<_CID; n++) {    CID 16 bits    }  }  OFDMA symbol 8 bitsoffset  Subchannel offset 6 bits  Boosting 3 bits 000: normal (notboosted); 001: +6 dB; 010: −6 dB; 011: +9 dB; 100: +3 dB; 101: −3 dB;110: −9 dB; 111: −12 dB  No. OFDMA 7 bits Symbols  No. Subchannels 6bits  Reception Coding 2 bits 0b00 - No repetition coding Indication0b01 - Repetition coding of 2 used 0b10 - Repetition coding of 4 used0b11 - Repetition coding of 6 used   } }

TABLE 4 Syntax Size Notes UL-MAP_IE( ) {   CID 16 bits    UIUC 4 bits  If (UIUC == 12) {  OFDMA symbol offset 8 bits  Subchannel offset 7bits  No. OFDMA Symbols 7 bits  No. Subchannels 7 bits  Ranging Method 2bits 0b00 - Initial ranging over two symbols 0b01 - Initial Ranging overfour symbols 0b10 - BW Request/Periodic Ranging over one symbol 0b11 -BW Request/Periodic Ranging over three symbols  reserved 1 bit  Shall beset to zero } else if (UIUC == 14) {  CDMA_Allocation_IE( ) 32 bits    else if (UIUC == 15) {  Extended UIUC variable dependent IE  } else { Duration 10 bits  In OFDMA slots  Reception Coding 2 bits 0b00 - Norepetition coding Indication 0b01 - Repetition coding of 2 used 0b10 -Repetition coding of 4 used 0b11 - Repetition coding of 6 used   }Padding nibble, if needed 4 bits Completing to nearest byte, shall beset to 0. }

The frame control header (FCH) preceding the DL-MAP is a header thatindicates coding information and a length of the DL-MAP. Table 5 shows aframe structure of the FCH.

TABLE 5 Syntax Size Notes DL_Frame_Prefix_Format( ) { Used subchannelbitmap 6 bits Bit #0: Subchannels 0-11 are used Bit #1: Subchannels12-19 are used Bit #2: Subchannels 20-31 are used Bit #3: Subchannels32-39 are used Bit #4: Subchannels 40-51 are used Bit #5: Subchannels52-59 are used Ranging_Change_Indication 1 bit Repetition_Coding_Indication 2 bit  00 - No repetition coding on DL-MAP01 - Repetition coding of 2 used on DL-MAP 10 - Repetition coding of 4used on DL-MAP 11 - Repetition coding of 6 used on DL-MAPCoding_Indication 3 bits 0b000 - CC encoding used on DL-MAP 0b001 - BCCencoding used on DL-MAP 0b010 - CTC encoding used on DL-MAP 0b011 - ZTCC used on DL-MAP 0b100 to 0b111 - Reserved DL_MAP_Length 8 bitsreserved 4 bits Shall be set to zero }

Table 6 shows an example of a neighbor advertisement (MOB_NBR-ADV)message as a broadcast message of a neighbor base station. A basestation periodically broadcasts information about neighbor base stationsvia the MOB_NBR-ADV message. A mobile subscriber station receives themessage and refers to it for scanning and handover.

TABLE 6 Syntax Size Notes MOB_NBR- ADV_Message_Format( ) { ManagementMessage 8 bits Type = 53 Skip-Optional-Fields 8 bits Bit [0]: if set to1, omit Operator ID field bitmap Bit [1]: if set to 1, omit NBR BS IDfield Bit [2]: if set to 1, omit HO process optimization field Bit [3]:if set to 1, omit QoS related fields Bits [4] to [7]: reserved If(Skip-Optional-Fields- [0]=0) { Operator ID 24 bits  Unique ID assignedto the operator } Configuration Change 8 bits Incremented each time theinformation for the associated neighbor Count BS has changed.Fragmentation Index 4 bits This field indicates the currentfragmentation index. Total Fragmentation 4 bits This field indicates thetotal number of fragmentations. N_NEIGHBORS 8 bits For (j=0 ;j<N_NEIGHBORS ; j++) { Length 8 bits Length of message informationwithin the iteration of N_NEIGHBOR in bytes. PHY Profile ID 8 bitsAggregated IDs of Co-located FA Indicator, FA Configuration Indicator,FFT size, Band-width, Operation Mode of the starting sub-channelizationof a frame and Channel Number if (FA Index Indicator == 1) { FA Index 8bits This field, Frequency Assignment Index, is present only the FAIndex Indicator in PHY Profile ID is set. Otherwise, the neighbor BS hasthe same FA Index or the center frequency is indicated using the TLVencoded information. } if (BS EIRP Indicator == 1) { BS EIRP 8 bitsSigned Integer from −128 to 127 in unit of dBm. This field is presentonly if the BS EIRP indicator is set in PHY Profile ID. Otherwise, theBS has the same EIRP as the serving BS. } if (Skip-Optional-Fields[1]=0) { Neighbor BSID 24 bits  This is an optional field forOFDMA PHY and it is omitted or skipped if Skip Optional Fields Flag = 1.} Preamble 8 bits The index for the PHY profile specific preamble.Preamble Index Index/Subchannel Index is PHY specific for SCa and OFDMA.The value of Preamble Index shall be ignored and a value of 0x00 shallbe used for OFDM PHY. For the SCa and OFDMA PHY this parameter definesthe PHY specific preamble. For the OFDM PHY the 5 LSB contain the activeDL subchannel index. The 3 MSB shall be reserved and set to 0b000. if(Skip-Optional- Fields[2]=0) { HO Process Optimization 8 bits HO ProcessOptimization is provided as part of this message is indicative only. HOprocess requirements may change at time of actual HO. For each Bitlocation, a value of 0 indicates the associated reentry managementmessages shall be required, a value of 1 indicates the reentrymanagement message may be omitted. Regardless of the HO ProcessOptimization TLV settings, the target BS may send unsolicited SBC-RSPand/or REG-RSP management messages. Bit #0: Omit SBC-REQ/RSP managementmessages during current reentry processing Bit #1: Omit PKM-REQ/RSPmanagement messages during current reentry processing Bit #2: OmitREG-REQ/RSP management messages during current reentry processing Bit#3: Omit Network Address Acquisition management messages during currentreentry processing Bit #4: Omit Time of Day Acquisition managementmessages during current reentry processing Bit #5: Omit TFTP managementmessages during current reentry processing Bit #6: Full service andoperational state transfer or sharing between serving BS and target BS(ARQ, timers, counters, MAC state machines, etc. Bit #7: Reserved } if(Skip-Optional-Fields- [3]=0) { Scheduling Service 4 bits Bitmap toindicate if BS supports a particular scheduling service, 1 Supportedindicates support, 0 supports not support bit 0: Unsolicited GrantService (UGS) bit 1: Real-time Polling Service (rtPS) bit 2:Non-real-time Polling service (nrtPS) bit 3: Best Effort value of ?000?indicates no information on service available Available Radio Resource 4bits Percentage of reported average available subchannels and symbolsresources per frame 0000: 0% 0001: 20% 0010: 40% 0011: 60% 0100: 80%0101: 100% 0110-1110: reserved 0110-1110: reserved value of 1111indicates no information on service available Reserved 8 bits Shall beset to zero } DCD Configuration 4 bits This represents the 4 LS bits ofthe Neighbor BS current DCD Change Count configuration change count UCDConfiguration 4 bits This represents the 4 LS bits of the Neighbor BScurrent UCD Change Count configuration change count TLV Encoded Neighborvariable TLV specific information } }

Table 7 and Table 8 are embodiments of a basic capability request(SBC-REQ) message and a basic capability response (SBC-RSP) message,respectively. The mobile subscriber station having received the DL-MAPand UL-MAP executes ranging for a network access procedure and transmitsan SBC-REQ message to the base station to initiate a negotiation forbasic capability. In response to the negotiation, the base station sendsan SBC-RSP message about a portion coinciding with its performance.

TABLE 7 Syntax Size Notes SBC-REQ_Message_Format( ) { Management MessageType = 26 8 bits TLV Encoded Information variable TLV specific }

TABLE 8 Syntax Size Notes SBC-RSP_Message_Format( ) { Management MessageType = 27 8 bits TLV Encoded Attributes variable TLV specific }

Once the negotiation for basic capability is completed, the mobilesubscriber station executes a registration procedure via a registrationrequest (MOB-REG-REQ) message and a registration response (MOB-REG-RSP)message. Table 9 and Table 10 show examples of the MOB-REG-REQ andMOB-REG-RSP messages, respectively.

TABLE 9 Syntax Size Notes REG-REQ_Message_Format( ) { Management MessageType = 4 8 bits Downlink Channel ID 8 bits TLV Encoded Informationvariable TLV specific }

TABLE 10 Syntax Size Notes REG-RSP_Message_Format( ) { ManagementMessage Type = 5 8 bits Uplink Channel ID 8 bits TLV Encoded Informationvariable TLV specific }

Media independent handover (MIH) technology will now explained. Anobject of an IEEE 802.21 system, in progress for the internationalstandardization of inter-heterogeneous-network media independenthandover, is to enhance user convenience for mobile terminal devices byproviding seamless handover and service continuity between heterogeneousnetworks. An MIH function, event trigger, command service andinformation service (IS) are defined as basic requirements of the IEEE802.21 system.

A mobile subscriber station is a multi-node that supports at least oneinterface type, wherein an interface can be implemented in varioustypes. Possible interface types include a wire-line type interface suchas an IEEE 802.3-based Ethernet, wireless interface types based on IEEE802.XX including IEEE 802.11, IEEE 802.15, IEEE 802.16 or the like, andinterfaces defined by a cellular standardization organization such as3GPP and 3GPP2, for example.

FIG. 2 is an exemplary diagram of a multi-mode mobile subscriberstation. Referring to FIG. 2, a multi-mode mobile subscriber stationincludes a physical layer (PHY) per mode and a medium access control(MAC) layer per mode. Furthermore, an MIH layer lies below an IP layer.

Media independent handover (MIH) is defined between IEEE 802-seriesinterfaces or between an IEEE 802-series interface and a non-IEEE802-series interface, such as a 3GPP or 3GPP2 interface. Also, amobility supporting protocol of an upper layer such as a Mobile IP andsession initiation protocol (SIP) is supported for the seamless handoverservice.

A network registration procedure in initializing a broadband wirelessaccess system is explained as follows. FIG. 3 is a flowchart of a mobilestation initializing procedure in a broadband wireless access system.Referring to FIG. 3, once power of a mobile subscriber station is turnedon, the mobile subscriber station searches a downlink channel andacquires uplink/downlink synchronization with a base station via aDL-MAP and a UL-MAP (1). The mobile subscriber station adjusts uplinktransmission parameters by ranging with the base station via RNG-REQ andRNG-RSP messages, and the base station allocates a basic managementconnection identifier (CID) and a primary management CID to the mobilesubscriber station (2). The mobile subscriber station then negotiatesfor a basic capability with the base station via SBC-REQ and SBC-RSPmessages (3). Afterward, authorization is carried out on the mobilesubscriber station (4). The mobile subscriber station then performs aregistration procedure to the base station via REG-REQ and REG-RSPmessages, wherein the base station allocates a secondary management CIDto the mobile subscriber station managed by an Internet protocol (IP)(5). Once an IP connection is created (6), a current date and time areset (7). A configuration file of the mobile subscriber station is thendownloaded from a trivial file transfer protocol (TFTP) server (8), anda connection for a prepared service is created (9).

In media independent handover (MIH), an MIH function is placed below anIP layer and facilitates a handover handling process using a triggerevent and an input value from a second layer (Layer 2), such asinformation of other networks and the like. The MIH function can includeinput values based on user policy and configuration that may influence ahandover process. General interfaces are defined between the MIHfunction and a third layer (Layer 3) entity such as a mobile Internetprotocol (Mobile IP) and a session initiation protocol (SIP). Theseinterfaces provide information about a first layer (physical layer), thesecond layer (Layer 2) (MAC layer) and mobility management. The MIHacquires information about lower layers and a network with the help ofthe event and information service. Accordingly, the MIH function shouldbe placed in a higher layer to monitor and control statuses of otherlinks within the mobile subscriber station. FIG. 4 is a diagram offunctional entities and a transport protocol of a terminal including anMIH function and a network, in which dotted lines indicate a primitive,an event trigger and the like.

An event trigger for handover between heterogeneous networks isexplained as follows. For fast handover, a network layer needs to useinformation from a link layer to re-establish a connection as soon aspossible. A link layer event helps to estimate a user's movement and mayhelp a mobile subscriber station and network prepare handover inadvance. A trigger for handover may begin with a physical layer (PHY)and a medium access control layer (MAC). An origin of this trigger maybe a local stack or a remote stack. FIG. 5 is a diagram of a triggermodel.

An event trigger provides a state of a current signal, a state change ofanother network and an estimated change. The event trigger also providesinformation regarding a change between a physical layer and a mediumaccess control layer and attribute changes of a specific network. Eventtypes can be classified into the following: (1) PHY layer event; (2) MAClayer event; (3) Management event; (4) L3 event; and (5) Applicationevent.

Basic trigger events will now be explained. A “Link_Up” trigger eventoccurs when a Layer 2 (L2) connection is established on a specific linkinterface and when Layer 3 (L3) packets can be transferred from a higherlayer. In this case, it is decided that all L2 configurationsconfiguring the link are completed. Event origins are a Local MAC and aRemote MAC. Parameters are shown in Table 11.

TABLE 11 Name Type Description EventSource EVENT_LAYER_TYPE Origin fromwhich event is generated EventDestination EVENT_LAYER_TYPE Destinationto which event shall be delivered MacMobileTerminal MAC Address MACaddress of MSS MacOldAccessRouter MAC Address MAC address of old accessrouter MacNewAccessRouter MAC Address MAC address of new access routerNetworkIdentifier Media Specific Network Identifier usable in detectingchange of subnet IP_Renewal_Indicator Indicating necessity of changingtemporary IP address. 0: change unnecessary 1: change necessary

A “Link Down” trigger event occurs when an L2 connection is released ona specific interface and when it is no longer able to transfer L3packets. An event origin is a Local MAC. Parameters are shown in Table12.

TABLE 12 Name Type Description EventSource EVENT_LAYER_TYPE Origin fromwhich event is generated EventDestination EVENT_LAYER_TYPE Destinationto which event shall be delivered MacMobileTerminal MAC Address MACaddress of MSS MacOldAccessRouter MAC Address MAC address of old accessrouter ReasonCode Reason why link is released

A “Link Going Down” trigger event occurs when it is estimated that an L2connection is going to link down within a specific time. The “Link GoingDown” trigger event may be a signal for initializing a handoverprocedure. Event origins are a Local MAC and a Remote MAC. Parametersare shown in Table 13.

TABLE 13 Name Type Description EventSource EVENT_LAYER_TYPE Origin fromwhich event is generated EventDestination EVENT_LAYER_TYPE Destinationto which event shall be delivered MacMobileTerminal MAC Address MACaddress of MSS MacOldAccessRouter MAC Address MAC address of old accessrouter MacNewAccessRouter MAC Address MAC address of new access routerTimeInterval Time in msecs Estimated time for Link_Up ConfidenceLevel %Estimated level for Link_Down of link in a specific timeUniqueEventIdentifier Used in case that Event rollback occurs

A “Link Going Up” trigger event occurs when it is estimated that an L2connection is going to link up within a specific time. The “Link GoingUp” trigger event is used in case when a long duration of time isrequired for a network to be initialized. Event origins are a Local MACand a Remote MAC. Parameters are shown in Table 14.

TABLE 14 Name Type Description EventSource EVENT_LAYER_TYPE Origin fromwhich event is generated EventDestination EVENT_LAYER_TYPE Destinationto which event shall be delivered MacMobileTerminal MAC Address MACaddress of MSS MacOldAccessRouter MAC Address MAC address of old accessrouter MacNewAccessRouter MAC Address MAC address of new access routerTimeInterval Time in msecs Estimated time for Link_Up ConfidenceLevel %Estimated level for Link_Up of link in a specific timeUniqueEventIdentifier Used in case that Event rollback occurs

A “Link_Available” trigger event indicates that a new specific link isusable or available. Furthermore, the “Link_Available” event indicatesthe possibility that a new base station or access point (AP) or point ofattachment (POA) can provide a link having a better quality than that ofa base station or AP or POA currently accessed by a mobile subscriberstation. Event origins are a Local MAC and a Remote MAC. Parameters areshown in Table 15.

TABLE 15 Name Type Description EventSource EVENT_LAYER_TYPE Origin fromwhich event is generated EventDestination EVENT_LAYER_TYPE Destinationto which event shall be delivered MacMobileTerminal MAC Address MACaddress of MSS MacOldAccessRouter MAC Address MAC address of old accessrouter MacNewAccessRouter MAC Address MAC address of new access routerIP_Renewal_Indicator Indicating necessity of changing temporary IPaddress. 0: change unnecessary 1: change necessary

An information service for inter-heterogeneous-network handover will nowbe explained. A media independent information service (MIIS) provides asimilar frame network on a hierarchical heterogeneous network tofacilitate a search and selection of various kinds of present networks.Namely, the media independent information service (MIIS) providesdetailed information about a network needed to search and select anetwork and should be accessible from any kind of networks. The mediaindependent information service (MIIS) should include the followinginformation elements such as link access parameter, security mechanism,neighbor map, location, provider and other access information, cost oflink and the like.

FIG. 6 is a flowchart of a procedure for acquiring an informationservice according to a related art. Referring to FIG. 6, an MIH of amobile subscriber station (MS) transfers an MIH_info.request message toits MAC to request an information service (S610). The MAC of the mobilesubscriber station then transfers an information request frame to a basestation (BS) (S620). A MAC of the base station delivers the informationrequest from the mobile subscriber station to its MIH viaMIH_Info.indication message (S630). The MIH of the base station thendelivers a retained media independent information service to the MAClayer via a MIH_Info.response message (S640). This enables the MAC ofthe base station to send an information response frame in response tothe mobile subscriber station (S650). The MAC of the mobile subscriberstation receives the information response frame and delivers contents ofthe received information service to its MIH via an MIH_Info.confirmmessage (S660).

However, in the related art for the broadband wireless access system, amulti-mode mobile subscriber station attempting handover to a broadbandwireless access system from another interface network (e.g., IEEE802.11, 3GPP or 3GPP2), a mobile subscriber station attempting handoverto another base station in the same broadband wireless access system, ora mobile subscriber station executing an initial network accessprocedure within a base station of a broadband wireless access system,is unable to know whether an MIH capability of a base station isavailable. Accordingly, what is needed is an invention that resolves theproblems of the related art.

SUMMARY OF THE INVENTION

The present invention is directed to supporting handover of a mobileterminal.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the presentinvention is embodied in a method of supporting a handover of a mobileterminal, the method comprising performing a scan of a neighboringnetwork different from a current network of the mobile terminal todetermine the presence of an accessible link of the neighboring networkfor performing a handover, wherein the mobile terminal comprises aheterogeneous network handover module that is configured to provideconvergence of information from at least one network interface moduleassociated with one of a homogeneous and heterogeneous network into aunified presentation, and receiving an information message from theneighboring network, wherein the information message comprises aninformation element associated with whether the neighboring network iscapable of communicating with the heterogeneous network handover moduleof the mobile terminal.

In one aspect of the invention, if the neighboring network has theheterogeneous network handover capability then the mobile terminalcommunicates with the neighboring network using a medium access controlmanagement message. In another aspect of the invention, the methodfurther comprises providing a scan request from the heterogeneousnetwork handover module to a broadband wireless access network interfaceprior to performing the scan.

Preferably, the information message is received through a medium accesscontrol of the broadband wireless access network interface andcommunicated to the heterogeneous network handover module. Preferably,the information message from the neighboring network further comprisesat least one of an information service support indicator, an eventservice support indicator and a command service support indicator.Preferably, the information message is one of a broadcast message, aframe check header message, a registration response message, asubscriber station basic capability response message, and a neighborbase station broadcast message.

Preferably, the information element received by the medium accesscontrol of the mobile terminal is communicated to the heterogeneousnetwork handover module. Preferably, the medium access controlcommunicates to the heterogeneous network handover module via one of alink available message and a capability indication message.

In accordance with another embodiment of the present invention, a methodof supporting a handover of a mobile terminal comprises communicatingwith a current network, receiving a broadcast message from the currentnetwork comprising at least one of heterogeneous networks within aserving base station and heterogeneous networks within a neighboringbase station, and providing to a heterogeneous network handover moduleof the mobile terminal information associated with the heterogeneousnetworks within a serving base station and heterogeneous networks withina neighboring base station, wherein the heterogeneous network handovermodule is configured to provide convergence of information from at leastone network interface module associated with one of a homogeneous andheterogeneous network into a unified presentation.

In accordance with another embodiment of the present invention, a methodof supporting a handover of a mobile terminal comprises transmitting toa current network a request message comprising an information elementassociated with whether the mobile terminal supports a heterogeneousnetwork handover module that is configured to provide convergence ofinformation from at least one network interface module associated withone of a homogeneous and heterogeneous network into a unifiedpresentation, and receiving from the current network a response messagecomprising an information element associated with whether the currentnetwork is capable of communicating with the heterogeneous networkhandover module of the mobile terminal.

In accordance with another embodiment of the present invention, a methodof supporting a handover of a mobile terminal comprises receiving fromthe mobile terminal a request message comprising an information elementassociated with whether the mobile terminal supports a heterogeneousnetwork handover module that is configured to provide convergence ofinformation from at least one network interface module associated withone of a homogeneous and heterogeneous network into a unifiedpresentation, and transmitting to the mobile terminal a response messagecomprising an information element associated with whether a currentnetwork is capable of communicating with the heterogeneous networkhandover module of the mobile terminal.

In one aspect of the invention, if the current network has theheterogeneous network handover capability then the mobile terminalcommunicates with the current network using a medium access controlmanagement message. In another aspect of the invention, the methodfurther comprises receiving a scan request from the heterogeneousnetwork handover module of the mobile terminal through a broadbandwireless access network interface prior to receiving the requestmessage.

Preferably, the response message is transmitted through a medium accesscontrol of the broadband wireless access network interface. Preferably,the response message further comprises at least one of an informationservice support indicator, an event service support indicator and acommand service support indicator. Preferably, the response message isone of a broadcast message, a frame check header message, a registrationresponse message, a subscriber station basic capability responsemessage, and a neighbor base station broadcast message.

In accordance with another embodiment of the present invention, a methodof supporting a handover of a mobile terminal comprises communicatingwith the mobile terminal, and transmitting a broadcast message from acurrent network to the mobile terminal, the broadcast message comprisingat least one of heterogeneous networks within a serving base station andheterogeneous networks within a neighboring base station, wherein themobile terminal provides to a heterogeneous network handover module ofthe mobile terminal information associated with the heterogeneousnetworks within a serving base station and heterogeneous networks withina neighboring base station, wherein the heterogeneous network handovermodule is configured to provide convergence of information from at leastone network interface module associated with one of a homogeneous andheterogeneous network into a unified presentation.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. Features, elements, and aspects of the invention that arereferenced by the same numerals in different figures represent the same,equivalent, or similar features, elements, or aspects in accordance withone or more embodiments.

FIG. 1 is a diagram of a frame structure of an orthogonal frequencydivision multiple access (OFDMA) physical layer in a broadband wirelessaccess system.

FIG. 2 is a diagram of a protocol stack structure of a multi-mode mobilesubscriber station.

FIG. 3 is a flowchart of a network registration procedure ininitializing a broadband wireless access system.

FIG. 4 is a diagram of functional entities and a transport protocol of amobile terminal including an MIH function and a network.

FIG. 5 is a diagram of a trigger model.

FIG. 6 is a flowchart of a procedure for acquiring an informationservice according to a related art.

FIG. 7 is a flowchart of a method for transmitting a DL-MAP messageincluding MIH Capability from a base station in accordance with oneembodiment of the present invention.

FIG. 8 is a flowchart of a procedure for acquiring MIH Capabilityinformation of a base station via basic capability negotiation requestand response messages in accordance with one embodiment of the presentinvention.

FIG. 9 is a flowchart of a procedure for acquiring MIH Capabilityinformation of a base station via registration request and responsemessages in accordance with one embodiment of the present invention.

FIG. 10 is a flowchart of a procedure for acquiring MIH Capabilityinformation via a broadcast message of a base station in accordance withone embodiment of the present invention.

FIG. 11 is a flowchart of a procedure for acquiring MIH Capabilityinformation and information indicating whether an information service issupported via a neighbor advertisement (MOB_NBR-ADV) message inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to supporting a handover of a mobileterminal. Reference will now be made in detail to the preferredembodiments of the present invention, examples of which are illustratedin the accompanying drawings. Wherever possible, the same referencenumbers will be used throughout the drawings to refer to the same orlike parts.

The present invention relates to a method of acquiring information aboutMIH capability between a multi-mode mobile subscriber station (MSS) anda base station (BS) in a system where at least one of a broadbandwireless access network, a wired local area network (LAN), a wirelessLAN, and a cellular network is operated. No limitation is put on a typeof the LAN or cellular network. For example, the wired LAN network canemploy systems base on an IEEE 802.X system, the wireless LAN networkcan employ systems based on an IEEE 802.XX system, and the cellularnetwork can employ systems defined by a standardization organizationsuch as 3GPP and 3GPP2.

A currently accessed base station transmits MIH Capability informationto a multi-mode mobile subscriber station so that the multi-mode mobilesubscriber station can acquire MIH Capability information of a targetbase station belonging to a heterogeneous network the multi-mode mobilesubscriber station attempts to access. There are various kinds ofmethods for transmitting MIH Capability information. Therefore, inaccordance with the preferred embodiments of the present invention,different methods of transmitting MIH Capability information will beexplained in the following description.

In accordance with a first embodiment of the present invention, a basestation transmits a neighbor base station advertisement message(MOB-NBR-ADV) including MIH Capability information.

In accordance with a second embodiment of the present invention, a basestation includes MIH Capability information in a frame check header(FCH) to be transmitted. In accordance with a third embodiment of thepresent invention, a base station includes MIH Capability information inan information element of a DL-MAP to be transmitted.

In accordance with a fourth embodiment of the present invention, MIHCapability information is included in a basic capability request/basiccapability response (SBC-REQ/SBC-RSP) message communicated when amulti-mode mobile subscriber station negotiates with a base station forbasic capability information. In one aspect of the invention, themulti-mode mobile subscriber station and the base station negotiate witheach other for mutual MIH Capability.

In accordance with a fifth embodiment of the present invention, MIHCapability information is included in a registrationrequest/registration response (MOB-REG-REQ/MOB-REG-RSP) messagecommunicated when a multi-mode mobile subscriber station executes aregistration procedure to a base station. In one aspect of theinvention, the multi-mode mobile subscriber station and the base stationnegotiate with each other for mutual MIH Capability.

In accordance with a sixth embodiment of the present invention, a mobilesubscriber station acquires MIH Capability information via a beaconmessage from a base station.

A base station may not only provide MIH Capability information aboutneighboring broadband wireless access system base stations to currentlyaccessed mobile subscriber stations, but may also provide MIH Capabilityinformation about wireless LAN access points (APs) or points ofattachment (POAs) capable of signal reception and cellular basestations. This may be done via a neighbor base station advertisement(MOB-NBR-ADV) broadcast message. Preferably, this message may include anInformation Service (IS) Support field indicating whether acorresponding base station and APs or POAs can provide an informationservice acquired from an information service (IS) server to a mobilesubscriber station. Table 16 shows an example of a format that isappended to an MOB-NBR-ADV message to represent MIH Capabilityinformation about a neighbor base station and a wireless LAN POA orcellular system base station.

An MIH INFO bitmap newly appended to a previous MOB-NBR-ADV messagerepresents MIH Capability and IS Support about an available wireless LANPOA or a cellular system base station neighboring a broadband wirelessaccess network base station a mobile subscriber station is accessing. AnMIH INFO bitmap 2 indicates a presence or non-presence of MIH Capabilityand IS Support for a heterogeneous point of attachment located in thevicinity of neighboring broadband wireless access base stations, i.e., awireless LAN POA or cellular system base station. Preferably, the MIHINFO bitmap 2 may indicate information about a presence or non-presenceof MIH Capability and IS Support for a heterogeneous point of attachmentlocated in the vicinity of a homogeneous neighbor base station as wellas neighbor heterogeneous point of attachment information of a currentbase station.

A bit to include MIH Capability information of a current base station isadded, by which a mobile subscriber station newly entering a currentbase station area can acquire information indicating whether MIHCapability and an IS function of a current or neighbor base station canbe provided in a manner of receiving a downlink channel descriptor (DCD)message. The mobile subscriber station uses the information to acquire aburst file for decoding a broadcast message, obtain an originatinglocation of the MOB_NBR-ADV message from the DL-MAP and decode theMOB_NBR-ADV message as a broadcast message received from thecorresponding location. An MIH Unknown bit is added to the MIH INFObitmap 1 or 2 for indicating a base station of which the presence ornon-presence of MIH Enabled or MIH Disabled is unknown, i.e., basestations of which Capability is not confirmed. For example, if awireless LAN POA available for MIH INFO bitmap 1 is discovered andbitmap information such as [1] Available WLAN POA, [0] Available POA MIHEnabled and [1] Available WLAN POA MIH Unknown is received, the statusof the MIH Capability is unknown although a wireless POA enablinghandover exists in the vicinity of a current base station. Hence, ameaning of the MIH Enabled bit is not related.

TABLE 16 Syntax Size Notes MOB_NBR- ADV_Message_Format( ) { ManagementMessage 8 bits Type = 53 Skip-Optional-Fields 8 bits Bit [0]: if set to1, omit Operator ID field bitmap Bit [1]: if set to 1, omit MIH INFObitmap Bit [2]: if set to 1, omit NBR BS ID field Bit [3]: if set to 1,omit HO process optimization field Bit [4]: if set to 1, omit QoSrelated fields Bit [5]: if set to 1, omit Current BS INFO Bit [6]: ifset to 1, omit MIH INFO bitmap2 Bits [7]-[8]: reserved If(Skip-Optional-Fields- [0]=0) { Operator ID 24 bits  Unique ID assignedto the operator } Configuration Change 8 bits Incremented each time theinformation for the associated neighbor Count BS has changed.Fragmentation Index 4 bits This field indicates the currentfragmentation index. Total Fragmentation 4 bits This field indicates thetotal number of fragmentations. If (Skip-Optional-Fields- [1]=0) { MIHINFO bitmap 1 16 bits  [0] Available WLAN POA [1] Available WLAN POA MIHEnabled [2] Available WLAN POA MIH Unknown [3] Available WLAN POA ISSupport [4] Available 3GPP BS [5] Available 3GPP BS MIH Enabled [6]Available 3GPP BS MIH Unknown [7] Available 3GPP BS IS Support [8]Available 3GPP2 BS [9] Available 3GPP2 BS MIH Enabled [10] Available3GPP2 BS MIH Unknown [11] Available 3GPP2 BS IS Support [12]-[15]reserved } If (Skip-Optional-Fields- [5]=0) { Current BS MIH INFO 1 bit [0]: MIH not Supported [1]: MIH Supported Event Service Supported 1 bit 0: ES Not Supported 1: ES Supported Command Service 1 bit  0: CS NotSupported Supported 1: CS Supported IS Supported 1 bit  0: IS NotSupported 1: IS Supported } N_NEIGHBORS 8 bits For (j=0 ; j<N_NEIGHBORS; j++) { If (Skip-Optional-Fields- [5]=0) { MIH INFO bitmap 2 16 bits [0] Available WLAN POA [1] Available WLAN POA MIH Enabled [2] AvailableWLAN POA MIH Unknown [3] Available WLAN POA IS Support [4] Available3GPP BS [5] Available 3GPP BS MIH Enabled [6] Available 3GPP BS MIHUnknown [7] Available 3GPP BS IS Support [8] Available 3GPP2 BS [9]Available 3GPP2 BS MIH Enabled [10] Available 3GPP2 BS MIH Unknown [11]Available 3GPP2 BS IS Support [12]-[15] reserved } Length 8 bits Lengthof message information within the iteration of N_NEIGHBOR in bytes. PHYProfile ID 8 bits Aggregated IDs of Co-located FA Indicator, FAConfiguration Indicator, FFT size, Bandwidth, Operation Mode of thestarting sub-channelization of a frame and Channel Number if (FA IndexIndicator == 1) { FA Index 8 bits This field, Frequency AssignmentIndex, is present only the FA Index Indicator in PHY Profile ID is set.Otherwise, the neighbor BS has the same FA Index or the center frequencyis indicated using the TLV encoded information. } if (BS EIRP Indicator== 1) { BS EIRP 8 bits Signed Integer from −128 to 127 in unit of dBm.This field is present only if the BS EIRP indicator is set in PHYProfile ID. Otherwise, the BS has the same EIRP as the serving BS. } if(Skip-Optional- Fields[2]=0) { Neighbor BSID 24 bits  This is anoptional field for OFDMA PHY and it is omitted or skipped if SkipOptional Fields Flag = 1. } MIH Capability 1 bit  This is indication forMIH Capability 0: MIH Not Supported 1: MIH Supported Event ServiceSupported 1 bit  0: Event Service is Not Supported 1: Event Service isSupported Command Service 1 bit  0: Command Service is Not SupportedSupported 1: Command Service is Supported IS Supported This isindication for Information Service support 0: Media IndependentInformation Service is Not Supported 1: Media Independent InformationService is Supported Preamble 8 bits The index for the PHY profilespecific preamble. Preamble Index Index/Subchannel Index is PHY specificfor SCa and OFDMA. The value of Preamble Index shall be ignored and avalue of 0x00? 0 shall be used for OFDM PHY. For the SCa and OFDMA PHYthis parameter defines the PHY specific preamble. For the OFDM PHY the 5LSB contain the active DL subchannel index. The 3 MSB shall be reservedand set to 0b000. if (Skip-Optional- Fields[3]=0) { HO ProcessOptimization 8 bits HO Process Optimization is provided as part of thismessage is indicative only. HO process requirements may change at timeof actual HO. For each Bit location, a value of 0 indicates theassociated reentry management messages shall be required, a value of 1indicates the reentry management message may be omitted. Regardless ofthe HO Process Optimization TLV settings, the target BS may sendunsolicited SBC-RSP and/or REG-RSP management messages. Bit #0: OmitSBC-REQ/RSP management messages during current reentry processing Bit#1: Omit PKM-REQ/RSP management messages during current reentryprocessing Bit #2: Omit REG-REQ/RSP management messages during currentreentry processing Bit #3: Omit Network Address Acquisition managementmessages during current reentry processing Bit #4: Omit Time of DayAcquisition management messages during current reentry processing Bit#5: Omit TFTP management messages during current reentry processing Bit#6: Full service and operational state transfer or sharing betweenserving BS and target BS (ARQ, timers, counters, MAC state machines,etc. Bit #7: Reserved } if (Skip-Optional-Fields- [4]=0) { SchedulingService 4 bits Bitmap to indicate if BS supports a particular schedulingservice, 1 Supported indicates support, 0 indicates not support bit 0:Unsolicited Grant Service (UGS) bit 1: Real-time Polling Service (rtPS)bit 2: Non-real-time Polling service (nrtPS) bit 3: Best Effort value of0000 indicates no information on service available Available RadioResource 4 bits Percentage of reported average available subchannels andsymbols resources per frame 0000: 0% 0001: 20% 0010: 40% 0011: 60% 0100:80% 0101: 100% 0110-1110: reserved 0110-1110: reserved value of 1111indicates no information on service available Reserved 8 bits Shall beset to zero } DCD Configuration 4 bits This represents the 4 LS bits ofthe Neighbor BS current DCD Change Count configuration change count UCDConfiguration 4 bits This represents the 4 LS bits of the Neighbor BScurrent UCD Change Count configuration change count TLV Encoded Neighborvariable TLV specific information } }

A base station may inform a mobile subscriber station of availability ofits MIH Capability by including the information in a frame check header(FCH). Accordingly, the mobile subscriber station may acquire the MIHCapability information about the corresponding base station from an MIHCapability information element after receiving the FCH to decode adownlink frame of the base station. Moreover, the mobile subscriberstation may acquire information related to whether the base station canprovide an information service acquired from an information service (IS)server to the mobile subscriber station from an IS Supported informationelement. Table 17 shows an example of an available format, in which “MIHCapability” and “IS Supported” information elements are appended to anFCH message. Through this format, a base station can inform a mobilesubscriber station whether an MIH function and an information servicecan be supported to the mobile subscriber station.

TABLE 17 Syntax Size Notes DL_Frame_Prefix_Format( ) { Used subchannelbitmap 6 bits Bit #0: Subchannels 0-11 are used Bit #1: Subchannels12-19 are used Bit #2: Subchannels 20-31 are used Bit #3: Subchannels32-39 are used Bit #4: Subchannels 40-51 are used Bit #5: Subchannels52-59 are used Ranging_Change_Indication 1 bit Repetition_Coding_Indication 2 bits 00 - No repetition coding on DL-MAP01 - Repetition coding of 2 used on DL-MAP 10 - Repetition coding of 4used on DL-MAP 11 - Repetition coding of 6 used on DL-MAPCoding_Indication 3 bits 0b000 - CC encoding used on DL-MAP 0b001 - BCCencoding used on DL-MAP 0b010 - CTC encoding used on DL-MAP 0b011 - ZTCC used on DL-MAP 0b100 to 0b111 - Reserved DL_MAP_Length 8 bits MIHCapability 1 bit  0: MIH Not Supported 1: MIH Supported Event ServiceSupported 1 bit  0: Media Independent Event Service is Not Supported 1:Media Independent Event Service is Supported Command Service Supported 1bit  0: Media Independent Command Service is Not Supported 1: MediaIndependent Command Service is Supported IS Supported 1 bit  0: IS NotSupported 1: IS Supported reserved 2 bits Shall be set to zero }

A base station may include availability of its MIH Capability within aDL-MAP message and inform a mobile subscriber station of theavailability. The mobile subscriber station having received the DL-MAPmessage for synchronization with the base station may acquire the MIHCapability information about the corresponding base station. Preferably,the base station acquires an information service from an IS server andmay include an Information Service Support field, which indicateswhether the information service can be provided to the mobile subscriberstation, in the DL-MAP message. Table 18 shows an example of a formatthat may represent MIH Capability information added to one InformationElement (IE) included in a DL-MAP message. An MIH_Capability_IE notifiesthe MIH capability of the network. The MIH capability indicates that theMIH function messages can be exchanged with the BS by using the MACmanagement messages in order for the MS to access the services of theMIH function of the network. Furthermore, the MIH_Capability_IE notifiesthe types of MIH services supported by the MIH function of the networkthrough the current BS. The capability to provide the MIH function ofthe network refers to the BS being able to directly use the services ofthe MIH function, and the BS being able to access the MIH functionentity via the NCMS.

TABLE 18 Syntax Size Notes MIH_Capability_IE( ) { Extended DIUC 4 bitsMIH_Capability_IE = XX Length 4 bits Length = 0x01 MIH Capability 1 bit 0: MIH Not Supported 1: MIH Supported Event Service 1 bit  0: MediaIndependent Event Service is Not Supported Supported 1: MediaIndependent Event Service is Supported Command Service 1 bit  0: MediaIndependent Command Service is Not Supported Supported 1: MediaIndependent Command Service is Supported Information Service 1 bit  Thisfield indicates whether a corresponding base station can Support providean information service from an IS server. 0: IS Not Supported 1: ISSupported Information Service 8 bits ID

Parameters are used to notify whether the current BS can access the MIHfunction services via the NCMS. This applies to a situation where thecurrent BS has the capabilities of the MIH function. If the parameter isset to “1,” the MS can access the MIH function via the current BS andcan use the MAC management messages associated with the MIH (e.g.,MOB_MSMIH-REQ, MOB_MSMIH-RSP, MOB_BSMIH-REQ, MOB_BSMIH-RSP) tocommunicate with the MIH function. An Event Service Supported parameteris a parameter used to notify whether the MIH function, which can beaccessed using the BS, supports an Event Service (ES). A Command ServiceSupported parameter is a parameter used to notify whether the MIHfunction, which can be accessed using the BS, supports a Command Service(CS). An Information Service Supported parameter is a parameter used tonotify whether the MIH function, which can be accessed using the BS,supports an Information Service (IS).

TLV (type, length and value) is used for negotiating with a base stationfor functions associated with Media Independent Handover. In case that amobile subscriber station including an MIH layer performs an MIHfunction, the mobile subscriber station sets a corresponding bit totransmit to a base station. If the base station including an MIH layeris able to support this function, the base station sets the bit in aresponse message to be transmitted.

With regard to an information service, when attempting to receive theinformation service via a base station, a mobile subscriber station setsa corresponding bit to make a request. If the base station is able toprovide the information service to the mobile subscriber station bycommunicating with an information service server or by acting as theinformation service server, the base station responds by setting the bitto enable negotiation between the mobile subscriber station and the basestation.

Table 19 illustrates the MIH Capability information in a TLV format inthe SBC-RSP message or the REG-RSP message according to an embodiment ofthe present invention. As illustrated in Table 19, if the MS sets thecorresponding bit to “1” and sends a request based on the setting, thisindicates that the corresponding capability is supported by the MIH ofthe MS. If the BS sets the corresponding bit to “1” and sends a responseaccordingly, this indicates that the corresponding capability issupported by the MIH function of the network which encompasses the BS.Alternatively, a bit setting of “0” indicates that the capability is notsupported.

Preferably, Bit #0 indicates whether the MIH is supported by the MS orthe BS. Moreover, Bit #1 indicates whether the ES is supported, Bit #2indicates whether the CS is supported, and Bit #3 indicates whether ISis supported. In detail, Bit #3 inquires as to whether the BS has thecapability to receive the IS from the IS Server or whether the BS canperform the capabilities of the IS Server.

In addition, a different indication of Bit #0 is that if this indicatoris set and transmitted by the BS, the BS can access the MIH function viathe NCMS or the services of the MIH function can be provided by the BS.Furthermore, if the value of the indicator is set and transmitted to theMS, this indicates that the MAC management message associated with theMIH (e.g., MOB_MSMIH-REQ, MOB_MSMIH-RSP, MOB_BSMIH-REQ, MOB_BSMIH-RSP)can be used.

TABLE 19 Type Length Value Scope MIH 1 Bit #0: Media Independent REG-REQCapability Handover Support (MIH Capability) Bit #1: Event ServiceSupported REG-RSP Bit #2: Command Service Supported SBC-REQ Bit #3:Information Service Supported SBC-RSP Bit #4~7: Reserved

Table 20 and Table 21 show other formats capable of including MIHCapability, respectively. When executing a network reentry procedure toa target base station by attempting handover or after having completed aranging procedure with a target base station to which an initial networkentry procedure is executed, a mobile subscriber station may include itsMIH Capability information in an SBC-REQ message to be transmitted whennegotiating with the base station for basic capability and thentransmitting the message to the base station. Table 21 shows an exampleof an MIH Capability field that can be included in an SBC-REQ message ina TLV format. If MIH Capability is available, a target base stationtransmits an SBC-RSP message by setting an MIH Capability bit to 1. Inthis case, the MIH Capability bit is included in the TLV of the SBC-RSPmessage in a format shown in Table 20.

A mobile subscriber station may include its MIH Capability informationin a MOB-REG-REQ message to be transmitted for executing a registrationprocedure and then transmit the message to a base station. Table 20shows an example of an MIH Capability field that may be included in anREG-REQ message in a TLV format. If MIH Capability is available, atarget base station transmits an REG-RSP message by setting an MIHCapability bit to 1. In this case, the MIH capability bit is included inthe TLV of the REG-RSP message in a format shown in Table 20.

TABLE 20 Syntax Size Notes MIH Capability 1 bit 0: MIH Not Supported 1:MIH Supported Information Service 1 bit This field indicates whether acorresponding Support base station can provide an information servicefrom an IS server. 0: IS Not Supported 1: IS Supported

TABLE 21 Syntax Size Notes MIH Capability 1 bit 0: MIH Not Supported 1:MIH Supported

In performing a scan, a MAC layer of a mobile subscriber stationreceives a beacon message including MIH Capability information from abase station. Accordingly, the MAC layer of the mobile subscriberstation includes this information in a Link_Available trigger andinforms an MIH of the information.

Table 22 shows one embodiment for including MIH Capability informationin a Link_Available trigger.

TABLE 22 Name Type Description EventSource EVENT_LAYER_TYPE Origin fromwhich event is generated EventDestination EVENT_LAYER_TYPE Destinationto which event shall be delivered MacMobileTerminal MAC Address MACaddress of MSS MacOldAccessRouter MAC Address MAC address of old accessrouter MacNewAccessRouter MAC Address MAC address of new access routerIP_Renewal_Indicator Indicating necessity of changing temporary IPaddress. 0: change unnecessary 1: change necessary MIH Capability 0: MIHNot Supported 1: MIH Supported Event Service Supported 1 bit 0: MediaIndependent Event Service is Not Supported 1: Media Independent EventService is Supported Command Service 1 bit 0: Media Independent CommandService is Not Supported Supported 1: Media Independent Command Serviceis Supported IS Support This field indicates whether a correspondingbase station can provide an information service from an IS server. 0: ISNot Supported 1: IS Supported

After receiving the DL-MAP including MIH Capability information from abase station, a MAC layer of a mobile subscriber station delivers theMIH Capability information of the base station to its MIH via an“MIH_Capability.indication” primitive. One embodiment of the“MIH_Capability.indication” primitive will now be explained.

First, functions of the “MIH_Capability.indication” primitive will beexplained. A MAC layer of a mobile subscriber station delivers MIHCapability information of a target base station to its MIH via thisprimitive. The primitive is then delivered to an upper management entityfrom the MIH to deliver MIH_Capability information of a neighbor basestation to the upper management entity. The upper management entity maybe used to decide whether handover to a network supporting MIH is to beperformed. Moreover, the primitive can be directly delivered to theupper management entity by the MAC layer. The upper management entitymay use this information in deciding to perform handover with referenceto a possibility of the network supporting MIH.

Semantics of the “MIH_Capability.indication” primitive is represented asfollows.

MIH_Capability.indication { Source; Destination; LinkIdentifier; BS MIHCapability; BS Event Service Supported; BS Command Service Supported; BSIS Support }

TABLE 23 Name Type Description Source Event_Source DestinationEvent_Destination LinkIdentifier Network Identifier can be one ofdifferent 802 and cellular networks BS MIH Flag 0: MIH Capability NotSupported Capability 1: MIH Capability Supported BS Event Flag 0: MediaIndependent Event Service Service is Not Supported Supported 1: MediaIndependent Event Service is Supported BS Command Flag 0: MediaIndependent Command Service Service is Not Supported Supported 1: MediaIndependent Command Service is Supported BS IS Support Flag 0: IS NotSupported 1: IS Supported

In case of a broadband wireless access system, “BS MIH Capability” and“BS IS Support” parameters represent MIH Capability of a new basestation and the possibility of IS support, respectively. According toeach heterogeneous media, “BS MIH Capability” and “BS IS Support”parameters represent MIH Capability and the possibility of IS Support ofa POA of a wireless LAN (IEEE 802.11) system, a Node B of a 3GPP system,or a base station (BTS) of 3GPP2 system.

A time for generating the “MIH_Capability.indication” primitive isexplained as follows. If a MAC layer of a mobile subscriber stationreceives a beacon, DL-MAP or Neighbor Advertisement message containingMIH Capability information of a point of attachment, the“MIH_Capability.indication” primitive is generated to deliver theinformation to the MIH or upper management entity. If the MIH discoversthat a new network (e.g. IEEE 802.16, IEEE 802.11, 3GPP, or 3GPP2) hasan MIH function or that the new network supports an information service(IS), the “MIH_Capability.indication” primitive is generated to informan upper management entity of the discovered information.

An effect of receiving the “MIH_Capability.indication” primitive isexplained as follows. After receiving the primitive, the MIH or uppermanagement entity acquires the MIH Capability information of the targetbase station.

In accordance with the preferred embodiments of the present invention,methods for providing MIH Capability of a base station to a multi-modemobile subscriber station in a broadband wireless access system will nowbe explained. In the following embodiments, handover to an IEEE 802.16system from an IEEE 802.11 system is described. However, as mentioned inthe foregoing description, the present invention is applicable to asystem operating in at least one of a broadband wireless access network,a wireless LAN, and a cellular network. Therefore, handover to variouskinds of wireless LANs, cellular networks or other broadband wirelessaccess networks is enabled.

A method according to one embodiment of the present invention isexplained as follows. First, a base station initially includes MIHCapability and IS (Information Service) Support information within anInformation Element (IE) of a DL-MAP and then transmits the DL-MAP. Inthe method according to this embodiment of the present invention,handover from a wireless LAN is explained. Preferably, the wireless LANoperates in an IEEE 802.11 system.

FIG. 7 shows an example of a base station transmitting a DL-MAP byincluding MIH Capability information and IS Support information in theDL-MAP when a multi-mode mobile subscriber station currently operatingin an IEEE 802.11 system attempts handover to an IEEE 802.16 system andreceives the DL-MAP for MAC synchronization.

Referring to FIG. 7, an IEEE 802.11 MAC of a multi-mode mobilesubscriber station (MSS) measures a quality of a currently connectedlink by periodic or requested scanning. If the quality of the currentlyconnected link is degraded, a “Link_Going_Down” trigger is transmittedto the MIH of the MSS (S710). After searching for a new link, an IEEE802.16 MAC of the MSS transmits a “Link_Available” trigger to the MIH ofthe MSS (S720). The 802.16 MAC of the MSS then receives and decodes aDL-MAP, which is transmitted each frame. From the DL-MAP, the 802.16 MACof the MSS acquires MIH Capability information and IS Supportinformation of a target base station (S730). Subsequently, the 802.16MAC of the MSS delivers the MIH Capability and IS Support information ofthe target base station to the MIH of the MSS via a“MIH_Capability.indication” primitive (S740).

In case that a multi-mode mobile subscriber station attempts handoverfrom an IEEE 802.16 base station to another IEEE 802.16 base station, orthat an initial network entry procedure is executed by powering amulti-mode mobile subscriber station within an IEEE 802.16 base station,MIH Capability and IS support information may be acquired via a DL-MAPaccording to the example of FIG. 7.

A method according to another embodiment of the present invention isexplained as follows. Preferably, MIH Capability information and ISSupport information are acquired via SBC-REQ and SBC-RSP messages when amobile subscriber station negotiates with a base station for basiccapability.

In this embodiment of the present invention, handover to a wireless LANamong cellular networks, broadband wireless access networks, andwireless LANs is described. Preferably, the wireless LAN is an IEEE802.11 system.

FIG. 8 shows an example of a multi-mode mobile subscriber stationcurrently operating in an IEEE 802.11 system acquiring MIH Capabilityinformation and IS Support information via SBC-REQ and SBC-RSP messageswhen attempting handover to an IEEE 802.16 system and negotiating with abase station for basic capability.

Referring to FIG. 8, if the quality of a link the mobile subscriberstation (MSS) is currently connected to is degraded, an IEEE 802.11 MACof the MSS transmits a “Link_Going_Down” trigger to the MIH of the MSS(S810). After searching for a new link, an IEEE 802.16 MAC of the MSStransmits a “Link_Available” trigger to the MIH of the MSS (S820). TheMSS then receives a DL-MAP from a base station and executes MACsynchronization (S830). Afterward, the MSS receives a UL-MAP from thebase station (S840). Thereafter, the MSS transmits an RNG-REQ message(S850) to the base station, and the base station sends an RNG-RSPmessage in response (S860).

After receiving the RNG_RSP message, the MSS includes its MIH Capabilityinformation in an SBC-REQ message to be transmitted for negotiating forbasic capability and transmits the message to the base station (S870).In response, the base station includes its MIH Capability and IS Supportinformation in an SBC-RSP message and sends the corresponding message tothe MSS (S880). The MSS includes the MIH Capability information of thebase station in an “M_Basic_Capability_Nego.confirmation” primitive anddelivers it to the MIH of the MSS (S890). Therefore, the MIH of themulti-mode mobile subscriber station can recognize whether the basestation supports an MIH function and an Information Service function.Notably, in the steps S830 to S880, a primitive transferred between theIEEE 802.16 MAC and the MIH of the mobile subscriber station, andanother primitive transferred between the IEEE 802.16 MAC and the MIH ofthe base station are omitted.

In case that a multi-mode mobile subscriber station attempts handoverfrom an IEEE 802.16 base station to another IEEE 802.16 base station, orthat an initial network entry procedure is executed by powering amulti-mode mobile subscriber station within an IEEE 802.16 base station,MIH Capability and IS support information can be acquired via theSBC-REQ and SBC-RSP messages according to the embodiment shown in FIG.8.

A method according to another embodiment of the present invention isexplained as follows. Preferably, MIH Capability information and ISSupport information are acquired via REG-REQ and REG-RSP messages when amobile subscriber station executes a registration procedure to a basestation.

In this embodiment of the present invention, handover to a wireless LANamong cellular networks, broadband wireless access networks and wirelessLANs is described. Preferably, the wireless LAN network is an IEEE802.11 system.

FIG. 9 shows an example of a multi-mode mobile subscriber stationcurrently operating in an IEEE 802.11 system acquiring MIH Capabilityinformation and IS Support information via REG-REQ and REG-RSP messageswhen attempting handover to an IEEE 802.16 system and executing aregistration procedure to a base station.

Referring to FIG. 9, an IEEE 802.11 MAC of a multi-mode mobilesubscriber station (MSS) measures a quality of a link the MSS iscurrently connected to by periodic or requested scanning. If the qualityof the currently connected link is degraded, the IEEE 802.11 MAC of aMSS transmits a “Link_Going_Down” trigger to the MIH of the MSS (S901).After searching for a new link, an IEEE 802.16 MAC transmits a“Link_Available” trigger to the MIH of the MSS (S902). The MSS thenreceives a DL-MAP from a base station (BS) and executes MACsynchronization (S903). Afterward, the MSS receives a UL-MAP from thebase station (S904). Thereafter, the MSS transmits an RNG-REQ message(S905) to the base station, and the base station sends an RNG-RSPmessage in response (S906).

The MSS then sends an SBC-REQ message to the base station to negotiatefor basic capability (S907) and the base station sends an SBC-RSPmessage in response (S908). After receiving the SBC-RSP message from thebase station, the mobile subscriber station includes its MIH Capabilityinformation in an REG-REQ message to be transmitted for executing aregistration procedure and transmits the message to the base station(S909). Accordingly, the base station includes its MIH Capability and ISSupport information in an REG-RSP message and sends the message to theMSS in response (S910).

Having received the REG-RSP message from the base station, the mobilesubscriber station delivers an “M_Registration.confirmation” primitivecontaining the MIH Capability information of the base station to its MIH(S911). Through this, the MIH of the multi-mode mobile subscriberstation can recognize whether the base station supports an MIH andInformation Service function. In the steps S903 to S910, a primitivetransferred between the IEEE 802.16 MAC and MIH of the mobile subscriberstation, and another primitive transferred between the IEEE 802.16 MACand MIH of the base station, are omitted.

In case that a multi-mode mobile subscriber station attempts handoverfrom an IEEE 802.16 base station to another IEEE 802.16 base station, orthat an initial network entry procedure is executed by powering amulti-mode mobile subscriber station within the IEEE 802.16 basestation, MIH Capability and IS support information can be acquired viathe REG-REQ and REG-RSP messages according to the embodiment shown inFIG. 9.

A method according to another embodiment of the present invention isexplained as follows. In this embodiment of the present invention,handover to a wireless LAN among cellular networks, broadband wirelessaccess networks and wireless LANs is described. Preferably, the wirelessLAN network is an IEEE 802.11 system. Preferably, a mobile subscriberstation receives a broadcast message containing MIH Capability from abase station is.

FIG. 10 shows an example of a multi-mode mobile subscriber station (MSS)currently operating in an IEEE 802.11 system acquiring MIH Capabilityinformation via a broadcast message from an IEEE 802.16 base station(BS). The MSS includes the information in a “Link_Available” trigger tobe transmitted to the MIH of the MSS, and transmits the trigger whenscanning another interface network because of signal degradation of acurrent link.

Referring to FIG. 10, an IEEE 802.11 MAC of a multi-mode mobilesubscriber station measures a quality of a link the MSS is currentlyconnected to by periodic or requested scanning. If the quality of thecurrently connected link is degraded, a “Link_Going_Down” trigger istransmitted to the MIH of the MSS (S1010). A higher management entity orMIH of the MSS then directs an IEEE 802.16 MAC of the MSS to perform ascan to search for a usable or available base station (S1020). The IEEE802.16 MAC performing a scan process receives a broadcast message froman IEEE 802.16 base station (S1030). Thereafter, the IEEE 802.16 MACtransfers MIH capability information included in the broadcast messageto the MIH of the MSS via a “Link_Available” trigger (S1040).

In case that a multi-mode mobile subscriber station attempts handoverfrom an IEEE 802.16 base station to another IEEE 802.16 base station, orthat an initial network entry procedure is executed by powering amulti-mode mobile subscriber station within the IEEE 802.16 basestation, MIH Capability and IS support information can be acquired viathe SBC-REQ and SBC-RSP messages according to the embodiment shown inFIG. 8.

A method according to another embodiment of the present invention isexplained as follows. First, a base station includes its MIH Capabilityand information service (IS) Support information in a neighboradvertisement (MOB_NBR-ADV) message and transmits the message. A mobilesubscriber station acquires the information and uses it to decidewhether to execute handover.

Referring to FIG. 11, a multi-mode mobile subscriber station (MSS)currently operating in an IEEE 802.11 system executes a scan process forother interface networks because a signal quality of a current link isdegraded. In doing so, the multi-mode mobile subscriber station acquiresMIH Capability information by receiving the Neighbor Advertisement(MOB_NBR-ADV) message transmitted from an IEEE 802.16 base station (BS).The MSS then delivers the MIH Capability information and IS Supportinformation of a target base station to its MIH via anMIH_Capability.indication primitive. Preferably, this primitive can bedelivered to an upper management entity. In case of acquiring the MIHCapability information from the scan process, the MIH Capabilityinformation acquired from the MOB_NBR-ADV message can be delivered tothe MIH of the MSS via a Link_Available trigger.

An IEEE 802.11 MAC of a multi-mode mobile subscriber station measures aquality of a currently accessed link by periodic or requested scanning.If the quality of the currently accessed link is degraded, aLink_Going_Down trigger is transmitted to the MIH of the MSS (S1101).After searching for a new link, an IEEE 802.16 MAC transmits aLink_Available trigger to the MIH of the MSS (S1102).

Thereafter, the IEEE 802.16 MAC of the MSS receives and decodes aDL-MAP, which is transmitted each frame (S1103) from the base station.Furthermore, the IEEE 802.16 MAC checks an interval to know when adownlink channel descriptor (DCD) is transmitted (S1105). The mobilesubscriber station having received the DCD can acquire a burst profileused in coding a broadcast message by a current base station.Accordingly, the mobile subscriber station can decode a receivedbroadcast message using the burst profile. By receiving the DL-MAP(S1106), the MSS can check when a Neighbor Advertisement (MOB_NBR-ADV)message is transmitted in order to receive the message. MIH Capabilityinformation and IS Support information of the current base station areacquired by decoding the received Neighbor Advertisement (MOB_NBR-ADV)using a downlink burst profile acquired via the DCD (S1107). The mobilesubscriber station then delivers the MIH Capability information and ISSupport information of the current base station to its MIH via anMIH_capability.indication primitive (S1108), wherein the primitive canbe delivered to an upper management entity (S1108).

In case of attempting a handover from one IEEE 802.16 base station toanother IEEE 802.16 base station, or in case of executing an initialnetwork entry procedure by powering a multi-mode mobile subscriberstation within the IEEE 802.16 base station, the multi-mode mobilesubscriber station can acquire MIH Capability and IS Support informationvia a MOB_NBR-ADV message according to the embodiment shown in FIG. 11.

Accordingly, the present invention provides the following advantages.First, a multi-mode mobile subscriber station attempting handover to abroadband wireless access system from another interface network (e.g.,IEEE 802.11, 3GPP, 3GPP2), a mobile subscriber station attemptinghandover to another base station within the same broadband wirelessaccess system, or a mobile subscriber station executing an initialnetwork entry procedure within a base station of a broadband wirelessaccess system, acquires MIH Capability and IS Support information of atarget base station by attempting a connection to the base station,thereby easily recognizing the capability of the target base stationassociated with Media Independent Handover.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuredescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. A method of data communication in a mobile terminal for supporting ahandover of the mobile terminal, the method comprising: transmitting toa base station a request message comprising media independent handover(MIH) capability information which indicates whether the mobile terminalsupports an MIH function associated with handover between heterogeneousnetworks and a first indicator indicating whether the mobile terminalsupports an information service, the request message transmitted duringan initial network entry procedure for capability negotiation with thebase station; and receiving from the base station a response message inresponse to the request message, the response message comprising mediaindependent handover (MIH) capability information which indicateswhether the base station supports an MIH function associated withhandover between the heterogeneous networks, the response messagereceived during the initial network entry procedure for the capabilitynegotiation.
 2. The method of claim 1, wherein the request message is abasic capability request (SBC-REQ) message and the response message is abasic capability response (SBC-RSP) message.
 3. The method of claim 1,wherein the request message further comprises at least one of a secondindicator indicating whether the mobile terminal supports an eventservice and a third indicator indicating whether the mobile terminalsupports a command service.
 4. The method of claim 1, wherein theresponse message further comprises at least one of a first indicatorindicating whether the base station supports an information service, asecond indicator indicating whether the base station supports an eventservice and a third indicator indicating whether the base stationsupports a command service.
 5. The method of claim 1, wherein therequest message further comprises information about a type of MIHservice supported by the MIH function of the mobile terminal.
 6. Themethod of claim 1, wherein the response message further comprisesinformation about a type of MIH service supported by the MIH function ofthe base station.
 7. A method of data communication at a base stationfor supporting a handover of a mobile terminal, the method comprising:receiving from the mobile terminal a request message comprising mediaindependent handover (MIH) capability information which indicateswhether the mobile terminal supports an MIH function associated withhandover between heterogeneous networks and a first indicator indicatingwhether the mobile terminal supports an information service, the requestmessage received during an initial network entry procedure forcapability negotiation with the base station; and transmitting to themobile terminal a response message in response to the request message,the response message comprising media independent handover (MIH)capability information which indicates whether the base station supportsan MIH function associated with handover between the heterogeneousnetworks, the response message transmitted during the initial networkentry procedure for the capability negotiation.
 8. The method of claim7, wherein if the base station supports the MIH function then the mobileterminal communicates with the base station using a medium accesscontrol management message.
 9. The method of claim 7, furthercomprising: receiving a scan request from the mobile terminal through abroadband wireless access network interface prior to receiving therequest message.
 10. The method of claim 7, wherein the response messageis transmitted through a medium access control of the broadband wirelessaccess network interface.
 11. The method of claim 7, wherein theresponse message further comprises at least one of an informationservice support indicator, an event service support indicator and acommand service support indicator.
 12. The method of claim 7, whereinthe response message is one of a broadcast message, a frame check headermessage, a registration response message, a subscriber station basiccapability response message, and a neighbor base station broadcastmessage.
 13. The method of claim 7, wherein the request message furthercomprises at least one of a second indicator indicating whether themobile terminal supports an event service and a third indicatorindicating whether the mobile terminal supports a command service. 14.The method of claim 7, wherein the request message further comprisesinformation about a type of MIH service supported by the MIH function ofthe mobile terminal.
 15. The method of claim 7, wherein the responsemessage further comprises information about a type of MIH servicesupported by the MIH function of the base station.
 16. A mobile terminalsupporting a media independent handover, the mobile terminal comprising:a transmitter for transmitting to a base station a request messagecomprising media independent handover (MIH) capability information whichindicates whether the mobile terminal supports an MIH functionassociated with handover between heterogeneous networks and a firstindicator indicating whether the mobile terminal supports an informationservice, the request message transmitted during an initial network entryprocedure for capability negotiation with the base station; and areceiver for receiving from the base station a response message inresponse to the request message, the response message comprising mediaindependent handover (MIH) capability information which indicateswhether the base station supports an MIH function associated withhandover between the heterogeneous networks, the response messagereceived during the initial network entry procedure for the capabilitynegotiation.